Small digital cameras have become so inexpensive as to be offered on a wide range of portable and wearable devices from watches, to helmets, to computing tablets, to media players to cellular telephones of all kinds. Typical digital sensors have many limitations in the quality of the images that they can produce for still and video photography. Further limitations stem from the limits in digital camera cost and size. For CCD (Charge Coupled Device) and even more for CMOS (Complementary Metal Oxide Semiconductor)-based sensors, the sensor is unable to capture the full contrast between light and dark areas of many scenes. Smaller sensors have an even smaller contrast range than larger sensors.
The range in the irradiance of the scene being photographed often exceeds the ability of a typical digital camera sensor. While the irradiance of bright areas striking the sensor can be reduced using a shutter or optical device, this also reduces the irradiance of the dark parts of the scene. Similarly the irradiance of a dark scene can be increased with a larger lens or longer exposure but this can cause the bright areas to exceed the sensor's limits. The sensor is therefore unable to capture the brightest and the darkest parts of the scene simultaneously. In other words, the sensor is unable to capture the scenes full dynamic range. Therefore, scenes that contain both very bright (e.g. sunlight) and very dark (e.g. shadow) areas are challenging for such sensors. As a result, the details of either very bright or very dark areas are captured but not both. Significant information available in the scene is lost, finally resulting in a poor user experience in terms of image quality.
In order to compensate for the sensors, many cameras use a technique referred to as HDR (High Dynamic Range) photography or imaging. The full irradiance of the scene is captured by taking multiple images of the same scene with different exposure settings by changing a shutter speed or lens aperture. The images are then combined into a single HDR image that includes detail in both dark and light areas of the scene.